Soybeans and other plants are photoperiodic, meaning they can be forced to flower by controlling the duration of light and dark exposure. A growth chamber where temperature, humidity, and light duration are controlled can be used to effectively grow photoperiodic plants at a faster rate indoors than outdoors.
In a typical growth chamber, a single layer of plants is exposed to an artificial light. The artificial light is turned on to expose the plants to light and off to expose the plants to darkness. Providing a second layer of plants would allow growth chamber space to be used more efficiently where a first layer is exposed to light, a second layer is exposed to darkness, and the plants can be moved between the two positions.